“Gates then turned to me and told me that I had no idea who I was ‘messing’ with and that I had not heard the last of it,’’ the report said. “While I was led to believe that Gates was lawfully in the residence, I was quite surprised and confused with the behavior he exhibited toward me.’’

The Cambridge police report describes a chaotic scene in which the police sergeant stood at Gates’s door, demanded identification, and radioed for assistance from Harvard University police when Gates presented him with a Harvard ID. A visibly upset Gates responded to the officer’s assertion that he was responding to a report of a break-in with, “Why, because I’m a black man in America?’’

Said Bobo: “The whole interaction should have ended right there, but I guess that wasn’t enough. The officer felt he hadn’t been deferred to sufficiently.’’

Gates showed his Harvard identification and Massachusetts drivers license with his home address, Ogletree said, adding, “Even after presentation of ID, the officer was still questioning his presence.’’

Gates’s lawyer and Harvard colleague, Charles Ogletree, said what angered his client was that the police officer stepped inside Gates’s Ware Street house, uninvited, to demand identification and question him.

Neither Gates - who was named one of Time magazine’s most influential Americans in 1997 and now directs the W.E.B. Du Bois Institute for African and African American Research at Harvard - nor police would comment on the incident yesterday.

“It’s unbelievable,’’ said Lawrence Bobo, a Harvard sociologist who visited Gates at the police station last Thursday and drove him home after Gates posted the $40 bail. “I felt as if I were in some kind of surreal moment, like ‘The Twilight Zone.’ I was mortified. . . . This is a humiliating thing and a pretty profound violation of the kind of trust we all take for granted.’’

But the encounter is anything but over. Some of Gates’s outraged colleagues said the run-in proves that even in a liberal enclave like Harvard Square, even with someone of Gates’s accomplishments, a black man is a suspect before he is a resident.

It ended when Gates, 58, was arrested on charges of disorderly conduct in allegedly shouting at the officer; he was eventually taken away in handcuffs.

The scene - two black men on the porch of a stately home on a tree-lined Cambridge street in the middle of the day - triggered events that were at turns dramatic and bizarre, a confrontation between one of the nation’s foremost African-American scholars and a police sergeant responding to a call that someone was breaking into the house.

His front door refused to budge, which is why Harvard professor Henry Louis Gates Jr., just home from a trip to China filming a PBS documentary, set his luggage down and beckoned his driver for help.

When the officer repeatedly told Gates he would speak with him outside, the normally mild-mannered professor shouted, “Ya, I’ll speak with your mama outside,’’ according to the report.

Gates was arrested after “exhibiting loud and tumultuous behavior’’ toward the officer who questioned him, the report said.

Gates, who came to Harvard in 1991, was “shocked and dismayed by what happened to him,’’ Ogletree said.

“What we hope is the charges against Professor Gates will be dropped, because he certainly didn’t break the law while entering his own home,’’ Ogletree said yesterday by phone.

He would not say whether he thinks racial bias played a role in Gates’s arrest.

Harvard president Drew G. Faust said yesterday that she was “obviously very concerned’’ when she learned about the incident. “Professor Gates is not only a colleague but also a friend,’’ she said in a statement. “He and I spoke directly, and I have asked him to keep me apprised.’’

Harvard has grappled with the issue of racial bias in recent years, even appointing an independent commission last fall to look into how the university could create a more welcoming environment after some black students and faculty complained of unfair treatment by the university’s predominantly white police force. Faust said in the spring that she hopes to implement some of the report’s recommendations by September, but it is unclear what they would be.

The arrest of such a prominent scholar under what some described as dubious circumstances shook the campus.

“He and I both raised the question of if he had been a white professor, whether this kind of thing would have happened to him, that they arrested him without any corroborating evidence,’’ said S. Allen Counter, a Harvard Medical School professor who spoke with Gates Friday. “I am deeply concerned about the way he was treated.’’

Counter has faced a similar situation himself. The neuroscience professor, who is black, was stopped by two Harvard police officers in 2004 after being mistaken for a robbery suspect as he crossed Harvard Yard.

“This is very disturbing that this could happen to anyone, and not just to a person of such distinction,’’ Counter said. “It brings up the question of whether black males are being targeted by Cambridge police for harassment.’’

Police say they were simply responding to a call from a woman who suspected a crime was taking place.

When the front door would not open, even with the driver’s help, Ogletree said Gates walked around to the back door, unlocked it, shut off the alarm system, and tried to open the door from the inside. It still did not work, so he went back outside and, with the driver, pushed it in.

Gates immediately called Harvard’s real estate office to report the broken door. While he was on the phone, police Sergeant James Crowley arrived and asked Gates to step outside, said Ogletree. Gates, indignant, refused, telling the officer that he lived there and that he works at Harvard.

When Crowley asked for proof, Gates initially refused, according to the police report. But Ogletree said Gates cooperated fully, walking into his kitchen for his wallet. The officer followed.

Gates “did ask him some pointed questions, like: ‘Is this happening because you’re a white cop and I’m a black man? Is this why this interaction is still taking place?’ ’’ Bobo said. “Who’s not going to feel upset and insulted when a police officer won’t accept the fact that you’re standing in your own living room?’’

Gates asked the officer several times for his name and badge number to file a complaint as the officer left the house. The police report said that when Crowley walked out of the home, Gates followed and continued to accuse the officer of racism. Crowley then handcuffed him.

Gates initially resisted, according to police, asserting that he was disabled and would fall without a cane. The officer reentered the home to fetch a cane. Gates was then taken in a police cruiser to department headquarters, where he remained for four hours, Ogletree said.

Gates is scheduled to be arraigned on Aug. 26.

Maria Cramer of the Globe staff contributed to this report.

© Copyright 2009 Globe Newspaper Company.