NEW HAVEN, Connecticut (CNN) -- Raymond J. Clark III, charged with murder in the death of Yale graduate student Annie Le, was smart, amiable and loved his dog, say those who knew him.
Raymond Clark III was arrested Thursday and charged with murder in the death of Annie Le.
One researcher said he often went by the lab in the Yale School of Medicine building where Le was found strangled and stuffed in a wall. Lufeng Zhang worked with Clark, he said, and thinks the police may have the wrong man.
"He's a nice man, always," he said.
Clark, 24, the same age as Le, was a technician in the school of medicine's Animal Resources Center. While Le, who was pursuing a doctorate in pharmacology, conducted experiments on mice, Clark took care of the rodents and cleaned their cages.
Police will not say whether Clark and Le were acquainted or why they homed in on Clark after Le went missing September 8, less than a week before she was scheduled to marry a Columbia University graduate student who was her college sweetheart. Watch police announce arrest »
"They work in the same building, passed in the hallways," New Haven Police Chief James Lewis said of Le and Clark. "Anything beyond that, I won't talk about."
Though details of the investigation are scant, police said they arrested Clark on Thursday and charged him with Le's murder after collecting more than 250 pieces of evidence.
Clark was an honor student at Branford High School in suburban New Haven. He graduated in 2004, and according to the school's yearbook, he was a member of the Asian Awareness Club his senior year.
High school friend Lisa Heselin remembers Clark "as a jokester, kind of a class clown," she said. "Everybody knew him. Everybody liked him."
She and others who knew Clark in high school are shocked that he was arrested in connection with Le's murder, she said. Watch what acquaintances say about Clark »
"They can't believe it, and then, of course, you're reminiscing, like, 'Oh my God, remember when we went over to his house and we all hung out?' You don't expect somebody you grew up with to be involved in something like this," Heselin said.
Maurice Perry, who said he has been friends with Clark since first grade, told CNN on Thursday night that he doesn't believe his longtime pal is guilty.
"This is not the Raymond Clark that I know," he said. "I've known him so long, I just can't picture him doing something like this."
Asked if he ever knew Clark to be violent, Perry replied, "Not at all. I've known him to be outgoing, happy, athletic, fun. Violent, not at all."
Most of his current neighbors in Middletown, about 30 miles northeast of New Haven, said they moved in after Clark or knew him only in passing. Many said he shared the second-floor apartment with his girlfriend and a dog.
Police said he drove a Ford Mustang, which was seized as evidence.
Neighbor Ashley Rowe described Clark as "decent" and said he asked a lot of questions when he spoke to people and wanted to know their full names and where they were from.
Rowe also remembered the first time she met his dog.
"His dog was very excited and he was just like, 'Oh, don't worry. He's friendly.' You could pet him," she said. "Pretty much, he just loved his dog and he walked around with his dog all the time."
Police arrived at his apartment Tuesday night to collect DNA samples and released him into the custody of his lawyer early Wednesday. Neighbors say they didn't see him return to the apartment. See investigation's timeline »
Clark was arrested early Thursday at a Super 8 motel in nearby Cromwell.
There were reports that Clark was scheduled to wed his roommate and girlfriend, Jennifer Hromadka, also a lab technician in Yale's Animal Resources Center, in December 2011. CNN could not confirm the report, and an Internet wedding page purportedly announcing the impending nuptials had been taken down Thursday.
Hromadka's MySpace page was private as of Tuesday evening, but several media outlets reported she had posted messages about Clark last year after hearing a "rumor of a fling."
"My boyfriend, Ray, if you don't know him, has no interest in any of the other girls at [the Yale Animal Resources Center] as anything more than friends," she reportedly wrote.
She said Clark had a "big heart" and tried to see the best in people, even if he didn't always make the best decisions.
"He is a bit naive, doesn't always use the best judgment, definitely is not the best judge of character, but he is a good guy," she reportedly wrote."He thinks everyone deserves a second chance and has a hard time hurting people's feelings, and it takes him getting burned to learn." Watch reporter, profiler discuss case »
Perry, Clark's friend since first grade, said he hadn't spoken to Clark in some time, but would send him a letter.
"I have always wanted to catch up with him, but I didn't want this to happen for me to try to find out how he was doing," he said.
Clark is being held on $3 million bond, Lewis said, but he would not provide details of what prompted Clark's arrest or whether DNA linked Clark to Le's murder.
He said Clark's arrest warrant was sealed, so he was prohibited from discussing the evidence.
Yale President Richard Levin said the school's administration is "relieved" by the news of an arrest, but warned, "We must resist the temptation to rush to judgment."
CNN's Eliott C. McLaughlin, Mary Snow, Tom Foreman and Larry King contributed to this report.