More than 1,000 people have been killed in the US since December in three different types of killings, with the first reported killing of a woman in California being linked to a man who was killed by a suspected serial killer in the state in September.
The deadliest day of the week came in the middle of a day of mass demonstrations in California and a handful of other states that were seen as an effort by authorities to take down protesters, as well as a series of mass shootings.
Authorities have blamed the mass shootings on the “lone wolf” shooter who opened fire in a crowded movie theatre on Thursday evening.
The first murder on Friday was a woman who died at a hospital after she was shot and killed by her ex-boyfriend on Thursday night, police said.
The man accused of the crime is expected to be released after being detained in California on Saturday.
The mass shooting in California is believed to be the worst in US history, with more than 50 people dead.
On Friday, a mass shooting occurred in New York City, with at least 10 people shot dead in the city, which has seen the highest number of homicides in the country in recent years.
Authorities say two other people were wounded in the attack in Brooklyn, but there have been no confirmed casualties.
Police have said the shooter is still on the loose, but have yet to release his name or make an arrest.
Authorities in California are also looking into the death of a 25-year-old woman who was found dead in her apartment in Oakland, the state’s largest city, on Friday.
Authorities had not yet confirmed the cause of death but the victim’s boyfriend said she was found in the bathroom with multiple gunshot wounds, and the cause is under investigation.
“The investigation continues, but I’m sure the boyfriend of this young lady has answers,” Oakland Police Chief Sean Whent said.
“It’s a terrible situation for all of us, the people that live in the community.”