Yale University lifted its lockdown and declared the campus safe after seven hours of a search for a gunman who may never have actually been there in the first place.

According to NBC Connecticut, at 9:48 a.m., police received a very brief 911 call from an anonymous person who said his roommate was heading to campus with a gun. The caller said nothing more and hung up after only several seconds on the line.

At least two people also reported seeing a gunman on the school's Old Campus, which became the "hot zone," the area where the gunman was believed to be. State police, local police, campus police, SWAT teams and more were on the scene searching for the potential shooter, but found nothing.

New Haven Police Chief Dean Esserman said the 911 call and shooter report was probably a hoax. He said there is no room for law enforcement to take a chance on a report that serious, so police will continue their room-by-room search.

"We don't have the luxury of going on a hunch, so we are gong to run this down to ground all the way," he said.

Officer David Hartman, a New Haven PD spokesman, said the 911 caller did not ID himself and only uttered one sentence on the line. Attempts to find his identity were unsuccessful. However, Esserman said the search for the person who made the call is not over.

"I'm not, and Chief Higgins is not going to walk away and go home tonight until everybody we're responsible for keeping safe is safe," Esserman said in a news conference. "And thought it is starting to tilt in the direction of an innocent mistake, it started with a purposeful and malicious call and the New Haven Police are going to track down the person who made that call, we're going to find the person who made that call, we're going to put handcuffs on the person who made that call."

Yale police began a room-by-room search where they would slip their ID under the door before asking permission to enter. If needed, they would use keys to get in, but would still identify themselves.

The lockdown may be over, but the searching is not. Police believe the eyewitness accounts of the gunman were students spotting a police officer with a rifle and not realizing it. While police look for who was responsible for the call and for what triggered the eyewitness accounts, they will be thankful for no injuries or shots fired.

"Nobody has been hurt, nobody has been found, but the day is hardly over," Esserman said. "Because, until we are satisfied that perhaps a police officer was mistakenly seen with a gun, and not a civilian seen with a gun, we are going to err on the side of caution."

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