SAN ANTONIO – A 20-year-old man accused of accidentally shooting his mom in the head while playing with a gun early Saturday morning is facing a charge of aggravated assault with a deadly weapon.

According to an arrest affidavit, Mathew Canales, 20, was in his bedroom at the Sundance Apartments at 4615 Gardendale when he pulled out a firearm and began playing with it.

The affidavit said a witness told police he was smoking meth with Canales when Canales pulled out the gun. According to the affidavit, the witness said Canales told him not to worry because the gun's safety was on.

However, Canales pulled the trigger and a bullet went through the wall into his mother's bedroom, court documents state. Police said the witness told them Canales fired the gun a second time before Canales told him to leave.

The witness said he knew Canales' mother had been hit by a bullet, the affidavit said.

According to authorities, Canales called 911 and claimed that there was a drive-by shooting at his apartment complex and that he accidentally shot his mother while returning fire.

Canales' mother is not expected to survive and is being kept on life support until her daughter is able to fly in from Colorado, the affidavit states.