Police shot a man as he tried to behead his mother with a large axe in the street.
The son managed to hit his mother in the head and back with the axe before he was apprehended in San Jose, California.
Local paper The Mercury reported both the 26-year-old suspect and his mother are expected to survive the attack.
"There is little doubt in my mind that these officers prevented a homicide in the city," police chief Eddie Garcia told the paper, "and that these officers' actions saved a life today."
Police were called to reports someone was driving erratically on Wednesday morning.
When they arrived, they saw a woman running from her home as her son chased her with an axe.
As he swung the axe, one of the officers shot at him but he was still able to follow through on the swing and strike his mother.
The second officer also shot the son, who fell down.
When he defied the officer's commands as they approached, one officer deployed his Taser, which reportedly had little effect.
"In fact, the suspect pulled out some of the prongs that were attached to his body," Mr Garcia said.
The attacker allegedly grabbed the axe again and hit his mother in the head.
He was eventually subdued with the help of a third officer.
Mr Garcia told the Mercury the son had a history of mental illness.
The son and mother's identities have not yet been released.
