The gunman holding hostages today inside a real-estate office in a Valparaiso, Ind., shot himself twice in the head before emergency crews rushed him to hospital, The Associated Press reported.

He released his final two hostages before trying to kill himself, and he's now in critical condition.

"I just know the reason for him being there was a dispute over … somebody in the building, an employee in the building, owed him money. He believed that," police Sgt. Michael Grennes told the AP.

Gunfire broke out when police first arrived at the Prudential office shortly after 10 a.m. CT, Grennes told MSNBC.

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After a standoff that lasted several hours, police heard what they thought were two gun shots.

SWAT team members broke windows and rushed into the building, where they found the suspect.

Earlier, at least five hostages were allowed to leave the building, and negotiators from the Porter County sheriff's SWAT unit were in contact with the gunman, Grennes told MSNBC.

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The gunman went to the 21st Century real estate office Friday morning because he believes someone there owes him money, police told The Associated Press.

An agent who works in the building told the AP the dispute was over a real-estate transaction.

Nearby schools were on a modified lockdown following the incident and employees of some area businesses were ordered to evacuate as a precaution, while others were told to stay away from windows, the Times of Munster reported.

The FBI, Indiana State Police and officers from three local jurisdictions remained at the scene Friday afternoon, according to the Times.