A man was shot and killed by his 18-year-old son Monday night after he stormed into his ex-girlfriend's Lealman house, deputies said.

John Heisler, 46, showed up at his ex-girlfriend’s house in the 5000 block of 43rd Avenue N just after midnight. Deputies said he was wearing full black tactical gear, including a ski mask and thigh holsters, when he tried to break into the house through a front window.

Deputies said his ex-girlfriend, identified as Jolene Andrews, and her 47-year-old boyfriend, Alton Pyles, heard the crash and went outside to investigate. They encountered Heisler, who pointed his gun at them, deputies said.

Detectives say Andrews and Pyles quickly ran into the home but were followed inside by Heisler. They tried to close the front door to keep him out, but he forced his way inside.

Investigators said Heisler grabbed Andrews and tried to force her to the ground. Andrews later told deputies that this is when she realized the intruder was her ex-boyfriend, as she recognized his voice and a tattoo on his arm.

Pyles called for help, which is when Heisler’s 18-year-old son, Malachi, opened his bedroom door and saw his father pointing a gun at his mother. Deputies said Heisler then turned the gun towards his son.

That’s when detectives say Malachi Heisler fired his weapon, hitting Heisler in the upper body.

"It's not something you prepare for," Malachi Heisler said on Tuesday. "You don't expect a burglary every day. You don't expect the person to be who it is."

John Heisler was pronounced dead at the scene. Deputies said they later determined his weapon was a BB gun.

"He pointed it at my mother first," Heisler said. "Then when I came out of the room, he pointed it at me. So picture in my head - it was a standoff between me and him."

Investigators say Andrews had obtained a temporary injunction against John Heisler in April, and she had been awarded an extension on the injunction through May 2016.

Officials said Heisler had broken into the home in April. They said he wasn't charged for that, because it was technically his own house, as he'd only recently left after an arguing.  However, Heisler, who was a convicted felon, was arrested after guns were found in a safe.

Investigators say there had been no contact since that incident. They also said Heisler had previously exhibited signs of alcohol and drug abuse, and mental health problems.

Detectives say Heisler and Andrews’ 13-year-old daughter was also in the house at the time of the shooting.

The investigation continues.