A University of Oklahoma (search) student tried to buy fertilizer of the type used in the 1995 Oklahoma City bombing two days before he committed suicide using explosives outside a packed football stadium.

Police said Thursday that the attempted purchase raised the suspicions of an off-duty officer who happened to be in the feed store at the time. But though an investigation had began, authorities were not able to act swiftly enough to stop the student from taking his own life.

Joel Henry Hinrichs III (search) died Saturday when explosives — made of hydrogen peroxide, not fertilizer — strapped to his body detonated while he sat on a park bench about 100 yards from the stadium.

Nobody else was injured, and FBI and university officials have said there was no indication he tried to get in the stadium or that he had any links to terrorism.

Lt. J.D. Younger said Hinrichs tried to buy the ammonium nitrate fertilizer at the Ellison Feed and Seed store on Sept. 29. The store no longer carries that type of fertilizer.

The off-duty officer, whose name has not been released, followed Hinrichs from the store and wrote down his tag number, Younger said.

From there, police identified Hinrichs as an OU student and determined his address. A police bomb squad was also contacted, and the off-duty officer was planning to submit a written report Monday.

"Unfortunately the incident that occurred Saturday was before the information could be forwarded," Younger said.

Hinrichs' father, Joel Hinrichs Jr., said the FBI told him the bomb his son had was made of hydrogen peroxide. He said the FBI told him more high-density hydrogen peroxide was found in the apartment. He said he thinks his son wanted to commit suicide and didn't want to harm others.

Meanwhile, OU president David Boren (search) released a letter Thursday cautioning the news media and community from jumping to any hasty conclusions about the case.

"We believe that we should not judge others ... on the basis of color, race, gender, economic status or freely exercised religious beliefs," the statement read. "To rush to judge others or make assumptions about them on that basis is nothing short of prejudice."

It was not clear what Boren was referring to, but the statement went on to note that some people incorrectly concluded early on that the Oklahoma City bombing (search) was the work of a Middle Eastern terrorist.

"As we all now know, the person responsible was not someone from the Middle East but was Timothy McVeigh and at least one other American who assisted him," the statement read.

Police led Hinrichs' roommate and three other Muslim students from a party after Saturday's explosion, Ashraf Hussein, president of the Muslim Student Association (search), has said. All were later released.