ALAMEDA, California (KPIX) -- Police say a husband gunned down his entire family and his in-laws inside his Alameda home Wednesday night and investigators say four are dead, including a 6-year-old boy.
A one-year-old was fighting for his life Thursday night.
The incident happened around 9 p.m. Wednesday on Kitty Hawk Road in Alameda. Neighbors are in shock and disbelief.
Many of the area residents thought shots they heard that night were fireworks.Then officers started arriving and the gruesome details of what had happened began to unfold.
"They were a family of two kids. Two boys just like us," said a neighbor who gave her name as Diane.
She lives a few doors down from the home where a mother, her two sons and her parents were gunned down.
"Last night when this was all going down, we came out and somebody said get inside there's an active shooter," Diane said. "I said 'Oh my God it's William's house! What did you mean there's an active shooter?' I went inside and grabbed my baby. It was terrifying."
Neighbors and friends identified William as the 6-year-old who was killed in the home. Those who knew him are still trying to understand how a father could open fire on his family.
"When somebody was finally arrested, my husband said "It's Shane,'" Diane said. "I couldn't believe it. We were shocked. In complete shock. We thought there was a stranger that went into that house. Our mind didn't even go there -- that it could be him."
Police say the father-in-law managed to get out of the home to a neighbor's house for help. When officers arrived, they arrested 54-year-old Shane Killian.
"This is a sad and tragic incident," said Chief Nishant Joshi with the Alameda Police Department. "And I'll say this, these are the actions of a coward."
There was a vigil Thursday at a beach in Alameda for those who knew the family. People including William's friend from school also stopped by the home to leave flowers, cards and candles at a memorial. Coach Ray brought a bat and left William his last game ball.
"Just hug your children tonight and give him a big hug," said Coach Ray. "Hug your brother, hug your sister. I lost a sister. I know the feeling everybody in this thing is going through. There's so many people. Wow. It just sucks."
Police have not released a motive but they say they are talking with the suspect to find out what led to this tragedy.
As a mother, Diane can't imagine the horror the family experienced in the final moments of their lives.
"Unbelievable," she said. "Imagine what they must be thinking. Why is, what's happening to their mom? Why is their dad trying to hurt me?"