Washington’s Attorney General Bob Ferguson on Wednesday proposed the state ban assault weapons.

Ferguson said he hopes such a law could prevent mass shootings like the one in Mukilteo in July, where a man with a semi-automatic rifle killed three young adults and injured another at a party.

Police say Allen Christopher Ivanov, 19, used a recently-bought AR-15 rifle in the killing spree. He told investigators he was angry that his ex-girlfriend, Anna Bui, was moving on after the two broke up.

Bui was killed in the shooting, as were Jordan Ebner and Jacob Long. All three were 19 years old.

At a Seattle news conference Wednesday, Ferguson said he would offer a measure in the next legislative session to bar sales of AR-15 rifles and other assault weapons in Washington state. The bill would also allow only 10 rounds of ammunition in gun magazines.

There is currently no limit on magazine capacity in Washington, according to Ferguson’s office.

“Massacres like this have become all too common across our country,” Ferguson told reporters.

Ferguson was joined by a handful of Democratic state lawmakers and other local officials and community members.

The parents of Will Kramer, 18, who was injured in the Mukilteo shooting spoke in favor of Ferguson’s bill.

“I want to speak out against the disgrace and insanity of our government continuing to allow military-style assault rifles to be easily available for purchase despite the increasing frequency of these shootings,” said Kramer’s mother, Liz Raemont, at the news conference.

She later added: “They’re the weapon of choice of our country’s mass murderers.”

Other gun regulation advocates in Washington have been pushing a statewide initiative that would allow courts to temporarily suspend a person’s access to guns if there is evidence they’re a threat to themselves or others. The temporary gun bans are known as “extreme-risk protection orders.”

Initiative 1491 is on the November election ballot and has the support of Seattle entrepreneur Nick Hanauer.

Measures similar to I-1491 and Ferguson’s legislation have been proposed by state lawmakers in recent years, but have failed to pass the Legislature.

Ferguson’s bill will undoubtedly face similar opposition.

Seven states including California have some form of an assault weapon ban while two states regulate assault weapons without banning them, according to the Law Center to Prevent Gun Violence.

The Associated Press contributed to this report