The warning signs were evident, long before Benjamin Kenya Bishop committed an act many consider unthinkable, authorities said.
Tension was a way of life in the family's Oldsmar home for six years, and in one incident, Bishop, 18, tried to strangle his mother, deputies said.
In another, Bishop was shot with a stun gun after he became violent when deputies tried to take him into custody under the state's Baker Act.
Then, late Sunday night, Bishop went into the bedroom where his mother and her boyfriend were sleeping and shot them dead, deputies said.
Although patricide and matricide cases are rare, children who kill their parents usually have a history of threatening or harming them, said Kathleen Heide, a criminology professor at the University of South Florida.
"A prior history of violence, a prior history of drugs — all these factors increase the risk," said Heide, who was talking about matricide in general and not specifically about Bishop's case.
"They should be heeded and intervention is needed. If there's threats of violence, not only therapy is needed, but you have to make sure the home situation is safe."
Bishop was arrested about 2 a.m. Sunday morning at the Oldsmar home he shared with his mother, Imari Shibata, and her boyfriend, Kelley M. Allen. Bishop, who deputies said has a long history of drug abuse and mental health problems, has been charged with two counts of first-degree murder.
Children who kill their parents are typically male, Heide said, and the preferred weapon is a gun.
Bishop pawned electronic gadgets to get money for a $279 shotgun, which he couldn't buy himself because he was on probation for attacking his mother, Pinellas County Sheriff Bob Gualtieri said.
So Bishop asked a friend to buy the weapon, which he said he needed to protect himself from gang members he met during a 10-month drug rehabilitation program, Gualtieri said.
Heide said there are three common situations where children feel that killing their parents may be necessary.
A severely abused or neglected child will act against the parents out of terror or desperation, she said. Children with underlying mental illnesses are also known to commit patricide, as are anti-social children who see parents as an obstacle to more money or freedom.
Patricide is preventable if professional help is sought and the parties involved live separately until the situation can be mediated, Heide said.
Vicki Hummer, the director of trauma services at the Crisis Center of Tampa Bay, said parents who have children with mental health and drug problems are in an exhausting, difficult situation.
"Medicine, doctors and support can stabilize people for a long time and they can live productive lives," Hummer said. "But there's often not a cure. It's a chronic problem and it's exhausting for parents."
But if warning signs can be spotted early, she said, tragedy can be avoided. These include a change in moods, sleep patterns and increasing irritability.
Gualtieri said a series of arguments Saturday between Bishop, his mother and Allen apparently led to the slayings.
"There was what appears to be a triggering event," Gualtieri said. "His mother told him … that he needed to make sure he was taking his medication, needed to get a job and had to start paying rent. He felt that the medication was killing him, so he decided he was going to kill his mother and her boyfriend."
Hummer said those arguments could have pushed Bishop over the edge.
"For someone very fragile, that could be perceived as a form of rejection and it led to an extreme reaction," Hummer said.
Hummer said it appears that Shibata was "trying to do the right thing."
Bishop, who was taking medication for schizophrenia, was addicted to synthetic drugs such as bath salts and Spice, Gualtieri said. When he returned home in September after completing 10 months of drug rehab, Shibata and Allen got rid of all the knives in the house.
"He complained he couldn't even make a sandwich in the house because there were no knives," the sheriff said. "Obviously, they were very concerned about him and concerned about his behavior."
Shibata and Allen, both 49, lived together for about 10 months, Gualtieri said. Allen was Bishop's swimming coach and that's how Allen may have met Shibata, the sheriff said.
On Monday, Allen's fellow coaches at the Westchase Swim & Tennis Center continued to grieve for their colleague, who cared for the children he taught and drove them to excel.
"We're all in shock," said Kelly Shires, a manager at the center. "I'm not sure we know how to deal with it. It's just hard."
Shires said he and other coaches are still not sure how to tell the children in their classes about Allen's death. Some participants are as young as 6.
Allen thought that swimming would be therapeutic for Bishop.
"Kelley had an interest in helping Ben with some of his issues and got him involved in swimming," Shires said. "So Kelley Allen was trying to improve not only the swim team but his own personal life."