Police were investigating Monday an apparent murder-suicide in an upscale neighborhood of Silicon Valley that left six people dead, including at least three children, and another person critically injured.

Lt. Phil Cooke said the suspect appeared to be among the dead and it looked like a "family on family" incident.

A neighbor called police at about 8:30 p.m. Sunday to report that a woman was injured outside the townhome, which is located in the Santa Clara community of Rivermark, about 7 miles northwest of San Jose, Cooke said.

Authorities found five bodies with gunshot wounds when they arrived at the home — a boy and girl under 10 years old, two adult men and a young woman or teenager.

A toddler later died at the hospital. Another woman was in critical condition, Cooke said.

Cooke said two handguns were recovered at the scene.

"It looks like it was family on family, murder suicide and that all the people were connected," Cooke said. He said police were doing interviews to find out "how it all fits together and try to get some indication why this happened."

The lieutenant said investigators also were working to notify extended family and confirm identities before releasing any of the victims' names. They also planned to reach out to any schools that the children may have attended to dispatch grievance counselors.

Residents describe the community of Rivermark as relatively quiet. The area has a mix of townhomes and homes with manicured lawns, shopping centers and restaurants.

"It's the sleepiest little area. Nothing ever happens here," said Jackie Stewart, who walked with her husband from her nearby home over to the crime scene, cordoned off with yellow police tape.

Cooke said he can recall three other family shootings in the last several years in Santa Clara, a city of about 108,000.

In 2002, a woman killed her estranged husband, two daughters and herself in her home. In 2003, a man smothered and drowned his 3-year-old son and a 12-year-old stepdaughter in Santa Clara before jumping off a cliff in Santa Cruz. Also in 2003, a man shot his wife and three children who were visiting from Orange County.

Santa Clara was rocked by another shooting in November, when authorities say a Silicon Valley engineer opened fire at an office park hours after being fired from his job, killing three colleagues.