TBILISI, Georgia – A man arrested after a fatal shootout with police admitted in video footage shown yesterday to throwing a grenade during a May rally where President Bush was making a speech.

Vladimir Arutyunian’s alleged confession came as investigators found grenades and unspecified chemicals in his home on the outskirts of Tbilisi and tried to piece together his motivations in the incident that cast a shadow over a visit meant to showcase Georgia’s progress.

“I threw the grenade during Bush’s speech,” Mr. Arutyunian said from a hospital room, where he was being treated for wounds suffered during a shootout as police tried to arrest him late Wednesday. One policeman was killed, and the suspect fled into the nearby woods. He was captured about an hour later.

Other video footage released yesterday by Georgian authorities showed Mr. Arutyunian lying on a gurney being wheeled from the scene, one of his cheeks swollen and bloody.

Mr. Bush and Georgia’s president, Mikhail Saakashvili, were on the podium in front of a massive crowd in downtown Tbilisi when the live grenade was thrown. The grenade landed less than 100 feet from the podium but did not explode.

A preliminary investigation indicated the grenade’s activation device deployed too slowly to detonate, the FBI said.

Authorities have not commented on whether Mr. Arutyunian was connected to any separatist groups in Georgia’s Abkhazia region or Chechnya.

The American Embassy in Georgia said yesterday it “welcomes the news that the Georgian Ministry of Internal Affairs, through joint efforts with the Federal Bureau of Investigation, diligent detective work, and a strong commitment to solving this case, have taken into custody a suspect.” The embassy declined comment on whether the FBI was involved in the arrest.

Mr. Saakashvili thanked the police for the successful detention.

“Yesterday our security forces carried out a special operation to detain the suspect in the attempted terrorist act during the speech in Tbilisi on May 10 by President George Bush,” the president told the Imedi television channel from the Netherlands, where he was on vacation.

Mr. Saakashvili said the suspect “did not aim to kill the presidents but deliver a huge blow to Georgia’s international reputation and the prestige of our country. Thankfully, with God’s help, it did not happen.”

Georgian authorities released a photo of the suspect Monday and announced an $80,000 reward for information leading to his identification. Interior Minister Vano Merabishvili said yesterday that several people were claiming the reward.