A 7-year-old boy who was shot in the head when his mother opened fire at a Houston megachurch on Sunday has undergone at least two surgeries in 24 hours and “lost a major part of what makes us who we are,” his grandmother said in an update on Thursday.

The surgeries included removal of part of the frontal lobe of the brain and a portion of the skull, the grandmother, Walli Carranza, said in a post on Facebook. It included a jarring photo of the child from his hospital bed, where officials said he remained in critical condition. She said the boy was engaged in a “fight for life.”

Authorities said the boy, Samuel, was with his mother on Sunday when she entered the Lakewood Church in Houston, just after a service led by the televangelist Joel Osteen. The mother, Genesse Ivonne Moreno, opened fire with an AR-15 and was killed in a gunfight with two security guards, officials said. It is still unknown who fired the shots that struck Ms. Moreno’s son and injured a bystander, a 57-year-old man who has since been released from the hospital.

Interviews with people who know the family, police records, and legal documents from a divorce and custody battle filed by the child’s paternal relatives offered a window into Samuel’s troubled upbringing, beginning with his premature birth in 2016 when his mother was just six months pregnant.

His father, Enrique Carranza III, who is Ms. Carranza’s son, described him in the divorce case as a toddler who often hit and bit anyone who tried to touch him. Because he was kept inside most of the time, he did not see a bird or a tree until he turned three, his father told the court.

In a 74-page affidavit of her own, Ms. Carranza, who is a rabbi, wrote that her daughter-in-law had been diagnosed with schizophrenia and began to unravel after she stopped taking her medication during her pregnancy. She described Ms. Moreno after that as a detached parent who avoided eye contact with her son and referred to him as “the boy,” or “the child.”

A hearing on the family’s bid to be granted custody of the boy under a conservatorship had been scheduled for May.

Ms. Moreno’s behavior had become so erratic in recent months that many of her neighbors in Conroe, Texas, a small city near Houston, complained that she created an environment of fear in the otherwise quiet neighborhood. The Conroe Police Department recorded dozens of calls to the block where Ms. Moreno lived with her mother, based mainly on complaints about harassment, threats and disorderly conduct. Many of the calls came from Ms. Moreno herself, according to police call logs. But it appeared that the authorities were reluctant to intervene in what were seen as personal matters.

When Ms. Carranza contacted them in July 2020 and shared a trove of emails that she said caused her concern about her grandson’s safety, the police reviewed them and determined that “no offense has occurred,” according to the records.

The officer wrote that the local district attorney did not want to “accept harassment charges” because of the divorce fight between the couple.

A police department spokesman, Sgt. David Dickenson, said none of the numerous calls rose to an incident that would warrant police intervention.

“There was no information related by the complainants, by the neighbors that would give officers the authority to make arrests or mental health detention,” he said. “If there’s no violation of law, we don’t have the authority to do anything.”

In an interview, Ms. Carranza said that Ms. Moreno and her son made a good couple when they began dating despite the fact that he was Jewish and she was a practicing Muslim.

In the early days after their marriage in June 2015, Ms. Moreno “did beautifully” when she took her medication, Ms. Carranza said. But things changed when Ms. Moreno learned she was pregnant and stopped taking it, she said. She became violent and unstable and was admitted involuntarily for psychiatric treatment at a hospital in Houston, where she remained for several weeks.

During those early years, her daughter-in-law kept several guns around the house, including a handgun in Samuel’s diaper bag, Ms. Carranza said in an affidavit.

Unable to deal with what he described as his wife’s violent outbursts, Mr. Carranza said in court filings, he filed for divorce. The animosity between the two of them led to his losing track of his son, he said. During a divorce court hearing in 2021, he testified that he was not present during his son’s birth and learned about it only the next month.

“She told the hospital that I was dead,” he testified.

In her own affidavit, Ms. Moreno alleged that Mr. Carranza had been physically abusive during their marriage. “On numerous occasions,” she wrote, he “made me fear for my safety.”

Mr. Carranza said it appeared his wife, who was apparently living with her mother, was trying to keep him away from his son, but he was able to track them down three years after his birth.

“I found her and we spent about two months together every day,” he told the court.

He said he was horrified to learn that the boy was in a near feral state, unable to talk, prone to anger and still relying on a feeding tube to eat.

“He didn’t speak at all. He exhibited violence. I mean, you’d pick him up and he’d hit you in the face,” Mr. Carranza told the court. “He’s just making noises and you know; I’m saying stuff to him, but he was at least, you know, trying to say words.”

He said he took his son to various parks and beaches, providing what he described as Samuel’s first experience with a playground or the outdoors. Getting him to eat solid food, Mr. Carranza said, proved more challenging. The initial goal, he said, was to get the boy to “not upchuck at the sight of food.”

He also learned that there had been an attempt at an intervention much earlier. He testified that he learned that child welfare authorities in Texas had investigated allegations that the boy was born with drugs in his system but never informed Mr. Carranza of it because his wife had deliberately left his name off his son’s birth certificate.

Patrick Crimmins, a spokesman with the Department of Family and Protective Services, said on Friday that he could not comment on Samuel’s case because of privacy restrictions.

Mr. Carranza is currently serving a prison sentence of more than two years in Florida, according to inmate records, for failure to register as a sex offender. His mother said the case stems from a statutory rape case several years ago when, at 18, he had a relationship with an underage girl. Ms. Carranza said she believes her daughter-in-law reported her son to the authorities when he moved to Florida.

Officials have said Ms. Moreno appeared to have purchased the AR-15 used in the attack at the church in December, and that she also had brought with her a .22 caliber rifle concealed in a bag but did not use it.

The authorities have not said how she purchased the weapons.

Since the shooting, Ms. Carranza wrote in her Facebook post that Samuel’s heart had stopped several times, and doctors had been unable to determine if he had significant brain activity because his scalp tissue was too fragile to allow the attachment of the necessary wires.

Neighbors in Conroe have been waiting anxiously to learn of any update.

Farrah Signorelli, who lives three doors down from Ms. Moreno’s house, was the boy’s special education teacher.

She described him as a petite and frail child with curly hair who looked younger than most 7-year-olds. She said he was mostly unable to talk and struggled to make friends in his class, attended by other children with special needs. She said he often appeared hungry: His mother, she said, sent him to school with two or three chicken nuggets “at most.” She said she offered him goldfish snacks when he seemed to want more food. “We made sure he ate,” she said.

She said the boy had stopped attending school around the end of October. She spotted him on Halloween in the back of his mother’s vehicle and said she breathed a sigh of relief to see that he seemed to be OK.

The next time she heard about him, she learned that he had been shot at Lakewood Church.