The Boston man who allegedly shot two New York City police officers "execution-style" before killing himself Saturday had a strong bias against police, according to USA Today.

Ismaaiyl Brinsley, 28, shot his girlfriend Saturday morning before arriving in Brooklyn where he shot Wenjian Liu and Rafael Ramos, one of whom was killed instantly and the other died at a hospital.

Before shooting the officers, Brinsley allegedly posted on an Instagram account, dontrunup.

Police are using his post as part of the investigation and have established he had a strong bias against police, and was allegedly seeking revenge for the deaths of Michael Brown and Eric Garner.

Michael Brown was an unarmed African-American teen who was shot and killed by officer Darren Wilson in Ferguson, Missouri. Eric Garner was an unarmed African-American man who was choked to death by police on Staten Island. The grand juries in both cases did not indict the officers, which has caused an outpouring of protests across the country over the past two weeks.

Garner's last words before his death, "I can't breathe," have been used on social media as a hashtag, as well as been printed on signs and shirts in protests. Brown's alleged last actions, raising his arms in surrender, are also being used as a sign in protests and die-ins across the country.

The Instagram account Brinsley used has since been deactivated, but post that depicts a bias against police shows a picture of a silver handgun, USA Today reported.

The caption of the photo read, "I'm putting wings on pigs today. They take 1 of ours ... Let's take 2 of theirs. #Shootthepolice #RIPErivGardner #RIPMikeBrown This may be my final post ... I'm putting pigs in a blanket."

USA Today reported that police said they found a silver handgun by Brinsley's body.

The next post on the account, according to USA Today, showed what appeared to be a bloodstained pant leg, captioned: "Never had a hot gon on your waist and blood on your shoe ...you aint been through what I been through you not like me and I'm not like you."

The Instagram account was linked to a Facebook page that appeared to be Brinsley.

The last post read, according to USA Today, "I Always Wanted To Be Known For Doing Something Right....... But My Past Is Stalking Me And My Present Is Haunting Me."