A California man has been arrested on Thomas Caldwellmurder charges in the fatal shooting of his wife, his 6-year-old son and his in-laws.

Shane Parrish Killian, 54, was arrested Wednesday night in the domestic shooting at his home in Alameda in the San Francisco Bay Area, police said.

Killian's 1-year-old son also was shot and was in critical condition at a local hospital.

Jail records show that Killian is being held without bail on charges of first-degree murder, assault with a firearm and child abuse. His arraignment is set for Friday.

No attorney is listed for him in court records.

Police found multiple firearms at home

Police found multiple firearms at Killian's home when they arrived at the scene, agency spokesperson Sarah Henry told USA TODAY Thursday.

Henry said the department hasn't yet determined a motive or what events led to the shooting.

"This is a tragic and sad incident, and I'll say this, these are the actions of a coward," Alameda Police Chief Nishant Joshi said at a news conference Thursday.

Joshi got emotional during the news conference.

"Our officers are hurt, they're professionals but they're also human beings," Joshi said. "They are doing the best they can but they're going to stay focused on making sure this family sees the justice they deserve."