"All indications point to a criminal act by an apparently emotionally disturbed individual", Abella told a news conference.
But hours later, the IS claimed responsibility in a statement, saying "Brother Abu al-Kheir al-Arkhabili was able to immerse among a gathering of Christian fighters in the Resorts World Manila in Manila where he carried out killing and hurting until he died as a martyr".
"The lone gunman committed suicide by setting himself on fire in one of the rooms on the fifth floor of the Resort World Hotel", the National Capitol Region Police Chief Oscar Albayalde told reporters. "The safety and security of our guests and employees is always a top priority".
Chief Director General Ronald dela Rosa said they are not considering terrorism as the motive behind the shooting that happened at Resorts World Manila (RW) since the gunman, whom he described as Caucasian and tall, did not fire at people but only at the chips stockroom. He added the authority would instruct shopping malls and hotels to be stricter with their security and that protocols would be reviewed.
Philippine government forces have been battling ISIS-linked militants on the southern island of Mindanao for control of the city of Marawi for more than a week.
Employees wait by the entrance to the Resorts World Manila complex on Saturday, June 3, 2017, a day after a gunman stormed the crowded Manila casino in Pasay city, southeast of Manila, Philippines.
The man then left the room and went upstairs to a hotel section of the complex, according to dela Rosa. The gunman then ran back to the 5th floor, holed himself up inside room No. 510 and set the room on fire.
"(He was) all dressed in black, burly, everything was covered, you can't even see his eyes", said Arguelle, who was about 9 meters (30 feet) from the gunman.
The bag of high-value gambling chips - with an estimated worth of 113 million to 130 million pesos, or more than $2 million - was found in a toilet.
The gunman initially disappeared into the chaos of smoke and running people, leading to a manhunt throughout the complex that ended just after dawn when he was found dead in a hotel room, according to Dela Rosa.
"We took out a ladder to save them".
"We believe that our security (measures) were enough, they will be reviewed", Reilly said when asked whether arrangements were adequate.
The injuries of survivors spoke to the terror inside the casino, with many breaking windows and jumping from the second floor to escape the fire and smoke. "I could not carry her".
"I would like to begin by addressing the terrorist attack in Manila", he said at the start of Rose Garden briefing to announced the US pull-out from the Paris climate agreement.
In a statement, Resorts World Manila, which bills itself as the country's largest casino, said the company "mourns with the families" and will offer support and assistance to the injured and families of the victims.
The unrest in Marawi had sparked fears that militants might attack elsewhere to divert the focus of thousands of troops trying to quell the siege.