HIGHLAND PARK, Illinois — The man detained by police in connection with the July 4 mass shooting at a parade planned the attack for weeks — and dressed as a woman to avoid detection, authorities said Tuesday.

Robert “Bobby” E. Crimo III, who was apprehended by police hours after the deadly shooting, climbed a fire escape to create a sniper’s nest to shoot down parade-goers Monday, authorities said.

“But we do believe that Crimo planned this attack several weeks in advance,” Chris Covelli, spokesman for the Lake County Major Crimes Task Force, told reporters on Tuesday.

Covelli also revealed that Crimo was dressed in women’s clothes, in part to distract from his facial tattoos. Authorities did not immediately give details about the clothes Crimo allegedly wore on Monday, or whether he or he wore a wig.

“During the attack, Crimo was dressed in women’s clothing and investigators believe he did this to hide his facial tattoos, his identity and help him escape,” Covelli said of the 21-year-old in custody.

That plan initially seemed to work, as Crimo reportedly walked undetected to his mother’s house, borrowed her car, and drove out of town.

“After the attack, Crimo left the roof, dropped his rifle and went into the crowd and he escaped,” Covelli said.

“He was totally absorbed in everyone as they ran around, almost as if he were an innocent bystander too.”

Investigators managed to piece together Crimo’s movements, based largely on video footage captured Monday in downtown Highland Park.

“He was seen on a video camera in the women’s clothing. The video camera played a tremendous role in how we could identify him, guiding both initially when he left,” Covelli said.

The sniper extorted more than 70 bullets from his perch on the roof and randomly picked victims downstairs, officials said.

Covelli said there was no immediate evidence that the gunman had been targeted by victims based on race or religion.

Highland Park is known as a heavily Jewish suburb, according to the Jewish Telegraphic Agency and Haaretz† Both news agencies noted that by some estimates, the area’s Jewish population is about a third of the total estimated population of 30,100†

“At the moment we have not developed a motive for him,” Covelli said.

“The shooting appears to be completely random. We have no information at this time to suggest it was racially motivated, motivated by religion, or (hatred of) any other protected status.”

The weapon was legally purchased in the state of Illinois, officials said. Covelli described it as “similar to an AR-15.”

“He brought a high-powered rifle to this parade, he entered the roof of a business through a fire escape and started opening fire on the innocent Independence Day visitors,” Covelli said.

Highland Park Mayor Nancy Rotering also revealed on Tuesday that she knew Crimo when he was with the Cub Scouts years ago.

She told NBC’s “TODAY” show that she is still baffled how anyone could unleash such violence. The eruption left six dead and dozens injured during the celebrations in the affluent Chicago suburb.

“I know him as someone who was a cub scout when I was the cub leader,” she said.

“And it’s one of those things where you step back and say, ‘What happened? How did someone get so angry? So hateful to then take it out on innocent people who were literally having a family day out?’ †

When asked about her memories of Crimo, the mayor replied succinctly, “He was just a little boy.”

In other developments arising from Monday’s mass shooting:

• The mayor on Tuesday condemned how the high-powered weapon used in murders could have been a legal purchase: “I don’t know where the gun came from, but I do know that it was obtained legally. And I think at some point this country needs to have a conversation about these weekly events where dozens of people have been killed with legally acquired weapons. If that’s what our laws stand for, I think we need to rethink the laws.”
• The number of people injured or injured in the chaos of Monday’s attack stands at 47†
• police is still asking people to get out of the center Highland Park on Tuesday as investigators continue to gather evidence.
• More details are emerging about the victims of Monday’s massacre. They include Nicolas Toledo, 78, and Jacki Sundheim.
• US Senator Dick Durbin, D-Ill., said Tuesday’s shooting marked the rise of a new, violent American tradition. tell MSNBC“Unfortunately, what happened here yesterday was the clash of two traditions: a wonderful tradition, of July 4 parades, and another terrible emerging tradition of mass shootings.” The Highland Park massacre follows mass shootings in Buffalo, New York, and Uvalde, Texas.

This is a story in development. Refresh here for updates.

Antonio Planas reported from Highland Park, Illinois, and Marlene Lenthang and David K. Li from New York City.