MARTINEZ -- A 22-year-old Clayton man charged with killing his father is believed to have attacked him four days before the 61-year-old was found dead in his home, a prosecutor said Tuesday.

Detectives believe Matthew Wester assaulted Richard Wester March 4 and that the father died March 8 of a traumatic chest injury after more than one of his ribs were fractured, causing blood to pool in his chest.

Police were called to the Wester home on rural Meadow View Lane the morning of March 8 after a 911 caller reported that Richard Wester, 61, was not breathing. It does not appear that the elder Wester sought medical treatment after the assault, a prosecutor said.

Matthew Wester stood silent during his brief court appearance Tuesday in which he was arraigned on charges of murder and assault with force likely to cause great bodily injury. The charges against the son do not mention that a weapon was used.

The 22-year-old, who is listed in court papers at 5-foot-10 inches tall and weighing 270 pounds, was "prone to rage" and suffers from Asperger's syndrome, according to a restraining order the father obtained against the son in June 2010.

The father wrote in the restraining order application that his son, upset over having to live in a group home, punched and kicked him, spit in his face, waved a knife and destroyed furniture. The restraining order expired in June 2011.

Matthew Wester is being jailed in lieu of $1.08 million bail, according to the Contra Costa County Sheriff's Office. He returns to court on March 19 at 1:30 p.m. for further arraignment and plea entry.

Contact Malaika Fraley at 925-234-1684. Contact David DeBolt at 925-943-8048. Follow them at Twitter.com/malaikafraley and Twitter.com/daviddebolt.