Police said Alfredo Graspelas, 54, a widower, of 363 Sandico street, Tondo was killed by a gunshot in the nape. The bullet exited his right eye.
Witnesses said the gunman, aided by two male accomplices, escaped by blending in with the panicking crowd after the shooting.
Police recovered a slug from a caliber .45 pistol near the victims body.
Investigation showed the shooting happened at about 9:30 a.m. inside a local cockpit (tupada) along Sto. Niño street corner Morga Extension in Tondo.
Police said the victim was attending to a fighting cock when the gunman approached him from behind and shot him pointblank at the back of his head.
Witnesses described the gunman as between 35 and 40 years old, wearing a black jacket, a striped T-shirt and his face partly hidden under a bullcap.
After the shooting, the gunman removed his jacket and handed it over to a male companion while another escorted him out of the cockpit.
The three suspects casually walked away from the crime scene amid the chaos created by scampering bettors.
Police suspected the gunman was a hired killer based on how composed he was before and after the killing.
"The witnesses said the hit was executed so casually. The gunman was cool and collected throughout the incident," a police investigator said.
Witnesses said the victim, who was also a fruit dealer, had been a regular bettor at several cockpits.
Police were also told the victim was a cockfight financier, but had incurred debts from a number of creditors.
Investigators suspect that the victim may have earned the ire of one of his creditors.
However, the victims 15-year-old only daughter said her father had never intimated to her that he has an enemy.