Dallas (CNN) -- Officials said Tuesday that "spotty" communications over 15 hours preceded a 44-year-old man's fatal fall from a 15-story crane at Southern Methodist University, but offered no explanation for what may have motivated him.
The incident began unfolding Monday morning, when SMU police called their Dallas counterparts "asking for assistance with an individual who jumped out of a vehicle and ran from them," said Dallas Police Department Assistant Chief Thomas Lawrence.
Patrol officers arrived and a tracking dog was brought in and established a track, but lost it, Lawrence told reporters.
An SMU officer then saw a man who had climbed into a crane on a construction site at the school "and was yelling down at the officers," Lawrence said.
When the man threatened to shoot an officer on the ground, police called in a SWAT team, which arrived at about 11:30 a.m., set up a perimeter and tried to communicate with the man, he said.
Over the next several hours, communications with the man were "spotty," he said.
"At times, he would communicate with us, at times he would not," Lawrence said. At one point, the man used the radio in the cab of the crane to talk with police, but "none of the communications we had with him were very productive," he said. "Obviously, we were trying to get him to agree to come down from the crane -- for his safety and for the safety of the community around."
As the day progressed, the temperature rose into the 90s; the cab contained only a small amount of water, Lawrence said. At one point, the man appeared to vomit, he added.
Unsure of whether the man was armed, police negotiated "well into the night," Lawrence said. But, when the man stopped communicating altogether after midnight, "we believed the situation was escalating," he said.
Police decided to send a team of SWAT officers up a ladder in the middle of the crane "to try to reestablish communications with him and to, hopefully, safely get him down from the crane so we could get him whatever help he needed," he said.
As the officers reached a platform behind the cab 150 feet above the ground, the man they were seeking turned and looked at them but said nothing, Lawrence said. "He did acknowledge he knew the officers were there," he said. "He then reached around and physically crawled outside the front of the crane where he had previously broken out the window and started spraying something at the officers." That something, he said, appeared to be a lubricant.
Then, the man abandoned the cab. "He initially put one leg outside the crane, then he put the second leg outside the crane," Lawrence said.
"At some point in that interaction there, he ended up getting in a position where he had slipped and was hanging from the window or either the window or window wipers of the front of the crane. Shortly after that, he fell from the crane and fell to his death."
Police identified the dead man as Lee Dell Thomas Jr., a 44-year-old man with a criminal record. Lawrence said he did not know what the record was for. He described Thomas as "a person of interest" in a previous robbery. "We don't know yet where the outcome of that will be," he said.
No weapon was found, he said.
Asked whether Thomas may have slipped, Lawrence said, "I don't know what was in his mind."
"None of us wanted it to end that way," the assistant chief told reporters. "But we have to try to resolve things the best way we can."
He described the outcome as "unfortunate."
SMU's vice president of external affairs, Brad Cheeves, said it was fortunate that the incident occurred on Memorial Day weekend, when the campus, which is located about five miles north of Dallas, was closed for regular activities. In addition, the standoff was confined to an area of athletic facilities, meaning that authorities did not need to close the entire campus, he said. "This was a situation that was probably not in the textbook," he said.
CNN's Nick Valencia and Ed Lavandera contributed to this report.