A Harvard undergraduate and his friend chased a would-be pickpocket through Harvard Yard early yesterday, tackling him before police arrived.

The man, who witnesses say tried to rob three undergraduate women, is Joseph Macchiarulo Jr., 21, of Brighton, according to the police.

Matthew C. Barber '02, of Pforzheimer, and his friend, Dane Benoit, both employees of Johnny's Luncheonette, had just finished their evening shift and were heading home through the Square around 1 a.m.

Three female undergraduates walked several paces ahead.

"This girl screamed and said her wallet was stolen," Benoit said.

Barber then noticed a blond-haired young man wearing a Nike jacket slinking away.

"He started walking pretty quickly. I started going after him," he said.

A chase began.

Barber and Benoit said they pursued the man through Boylston Gate and into the Yard. The two cornered the man in the small grassy area between Grays Hall and Wigglesworth Hall.

"By the time he got in front of the K entry, I just grabbed him and he fell," Barber said.

A proctor, Michael A. Armini, helped the two men hold the suspect.

Back on Mass Ave., one of the women called 911 on her cell phone, reaching the Cambridge Police Department.

Within a minute, CPD dispatchers were on the phone to the Harvard University Police Department (HUPD), which, in turn, dispatched its officers to the Yard.

At first, the description broadcast on the scanner was sketchy. A group of students were chasing a young man with long blond hair wearing a Nike jacket.

Suddenly, the scanner squawked with the news that two men were holding another on the ground between Wigglesworth and Grays Hall.

A swarm of officers covered the area within 20 seconds, and discovered Barber, Benoit and Armini holding the suspect on the ground.

As the victims gathered to tell their story to a Cambridge officer, the HUPD questioned the suspect, who was bent over a squad car and complaining loudly.

"They're trying to slam me for stealing their wallet," the suspect said. "They've got their wallet back."

Moments later, the CPD prisoner wagon arrived to transport the suspect to CPD headquarters.

As he was being led away, cursing and screaming, the suspect said, "Wait until my dad tells his lawyer."

A bemused Cambridge officer walked up to Barber and his friend, and asked who had chased the suspect.

"I did," responded Barber.

"Good job," the officer replied with a smile.

"This is the best story I've ever heard. He didn't even hesitate," Benoit told the police.

"It was instinct," Barber agreed.

After the suspect had been driven away, Barber and Benoit began to head for home. As they passed the three women, the women turned toward them and gave a chorus of "Thank you, guys!"

Said Armini, "It's a good example of students helping students."

The victim and her two friends declined comment.

--Garrett M. Graff contributed to the reporting of this article.