The guy suspected of killing 7 people and injuring dozens of others during a July 4 parade in Highland Park, Illinois, pre-planned the savage attack and dressed in women's clothing to disguise himself in an effort to evade capture ... police announced Tuesday.

During a news conference, Deputy Chief Christopher Covelli of the Lake County Sheriff’s Office said Robert Crimo wore his disguise to also cover up his tattoos ... as he squeezed off more than 70 rounds with a legally purchased high-powered rifle. Covelli noted that the death toll had gone up from 6 to 7 murder victims.

After the attack, Crimo allegedly dropped the rifle and fled from the roof of a business, from which he opened fire. During the ensuing chaos, he was able to blend in with the crowd thanks to his disguise, Covelli said.

Crimo then walked to his mother's nearby home and borrowed her Honda, cops said. He led police on a high-speed car chase that ended with him in handcuffs.

Cops believe the 21-year-old Crimo had been planning the attack for several weeks.

Crimo has yet to be charged in the mass shooting, but officials are expected to address that issue later this afternoon.