Maj. Talal Masri with the Palm Beach County Sheriff's Office said Friday that the gunman first shot the child at the Royal Palm Beach grocery store and that the 69-year-old woman then "instinctively jumps in and is trying to stop him." A struggle followed, Masri said.
The office tweeted a timeline of the shooting saying, "because of her brave actions, (Wall's) gun jams. After some struggling, he then ends up shooting the grandmother and then himself."
Sheriff's officials said they are prevented by law from releasing the names of the victims.
The randomness of the shooting at a popular supermarket chain, coupled with the uncertainty about the motive, thrust the crime into the national spotlight this week..
Authorities and Wall's family on Friday described him as a financially troubled individual who struggled with mental health disorders.
"He had mental issues. He wasn't taking care of himself," said Maia Knight, the sister of Wall's ex-wife, Monica Sandra Wall.
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Knight said Timothy Wall wasn't getting the help he needed for his mental illness, which she said was schizophrenia.
Serious mental illness is not a factor in most mass shootings or other mass killings, according to a recent study from the Columbia University Irving Medical Center and the New York State Psychiatric Institute.
"Emphasis on serious mental illness, such as schizophrenia or psychotic mood disorders, as a risk factor for mass shootings is given undue emphasis, leading to public fear and stigmatization," clinical psychologist Dr. Gary Brucato, one of the study authors, said in a news release at the time.
Wall married Monica Sandra Wall in 2003. The couple divorced in July 2017. They have a 14-year-old daughter.
A Palm Beach County circuit judge had allowed Timothy Wall to live in his marital home for a few months, but in May 2019, Monica Sandra Wall evicted her ex-husband from her Royal Palm Beach residence, court records show.
Monica Sandra Wall had previously reached out to law enforcement for help with her husband's mental illness, Knight said. The sheriff's office did not immediately respond to an email from the Palm Beach Post, part of the USA TODAY Network, asking whether Wall's ex-wife had indeed reached out.
The Sheriff's office said in a tweeted statement that there were warning signs leading up to the shooting: "The suspect was on Facebook saying he wanted to kill people and children."
Palm Beach County Sheriff Ric Bradshaw on Friday blasted the ex-wife and anybody who knew of Wall's unhinged social media raging but had failed to notify authorities.
"The real sad part of this, other than the fact that people are dead, is that there was a chance this could have been stopped," Bradshaw said. "You know why? The reason is, he's on Facebook. He has said, 'I want to kill people and children.'
Bradshaw said if the sheriff's office had been alerted to Wall's mental deterioration, then deputies could have confiscated any weapon in his possession.
"Obviously, there was some mental" instability, Bradshaw said. "If it sounds like I am angry, it's because I am."
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In a news conference Friday, authorities said Wall drove to the shopping plaza on a red scooter. Surveillance cameras caught him lurking in Walgreens and then again in Publix earlier in the morning, when he was apparently spooked off by a sheriff's deputy buying groceries.
Wall entered the Publix, holding a golf putter, using it as a walking stick. Surveillance-camera video shows Wall watching people across the produce section.
Thirty people were inside the Publix at the time of the shooting.
The first sheriff's deputy arrived three minutes after the attack and found all three people dead.
Royal Palm Beach is a middle-class suburb of 40,000 residents, about 12 miles from downtown West Palm Beach and 15 miles inland from Palm Beach.
Wall worked as a carpenter for a temp agency, had been legally evicted from his ex-wife's home and had filed for bankruptcy, records show. He appeared to be living at motels before the shooting, records show.
When he declared bankruptcy in January, he listed as his possession an APC 45 semi-automatic handgun meant for use by police and the military. The sheriff's office has not said what weapon Wall used in the shooting.
Sarah Brown, a hairstylist at Festive Cuts Beauty Salon in the Publix plaza, said customers and Publix employees took refuge at the business after the shooting.
"It was a normal day. I just had a consultation with my client, went to the back room to mix her color," she said in a Facebook post. "Then all of a sudden like a barrel of monkeys about 15 people – two even with carts ran into our small salon screaming 'Active Shooter! Everyone get in lock the doors get away from the windows!!!'"
She had the salon's receptionist held the door open as people rushed in, many panicked and hysterical.
"Unfortunately a couple people saw it happen and I can’t even imagine how horrific that was to witness," she said.
The tragedy is the second recent shooting at a retailer in Palm Beach County.
Samuel Rossetti of Palm Springs was shot dead while in the drive-through line of a Lake Worth Beach Starbucks in April, following a confrontation with the car in front of him. The driver of that vehicle is facing a first-degree murder charge.
In a video message released Friday, Royal Palm Beach Mayor Fred Pinto issued a statement regarding the Publix shooting: "What happened was too tragic, too familiar. Our hearts ache with the family. We share their pain, we share their anger."
Contributing: The Associated Press
This article originally appeared on Palm Beach Post: Florida Publix shooting: 'Brave' grandmother killed; motive unknown