A prisoner accused of killing an elderly man in broad daylight in December is facing new charges after allegedly using a makeshift knife to stab his cellmate multiple times.

Greg Hackett was charged with the murder of 89-year-old John Higby, who was shot and killed during an attempted robbery on Dec. 27, 2017, that occurred in the parking lot of the Dauphin Square shopping center.

The incident took place in the middle of the afternoon and left many residents of Midtown Mobile concerned as police searched to identify two potential suspects.

Greg Hackett, arrested for the 2017 murder of an elderly man in Mobile, is facing additional charges after stabbing an inmate at Mobile Metro Jail. (MCSO)

After a month in Mobile Metro Jail, though, corrections officers say Hackett used a homemade shank to stab a cellmate several times. Spokeswoman Lori Myles said the incident began with an argument, though Hackett nor the victim have disclosed what it was about.

The cellmate has so refused to press charges, but that hasn’t stopped jail officials from moving forward.

Warden Trey Oliver confirmed on Monday that Hackett would be facing additional charges of first-degree assault and promotion of prison contraband, both of which are felonies. He also said Hackett would be kept in an isolated area away from other prisoners moving forward.

However, this incident marks the second time in less than a month that a stabbing has occurred within Metro Jail. On Jan. 11, two prisoners were transported to area hospitals after 40-year-old Joshua Sherman Brown managed to sneak a knife into the facility while he was being processed.

Brown then used the knife to stab another inmate multiple times, though no life-threatening injuries were sustained by either inmate. At the time, Oliver said an investigation was being launched into how the weapon managed to get through Brown’s initial screening, though there have been no updates since.

Then just yesterday, another incident drew media attention to the goings-on inside Metro when a female inmate “ambushed” two corrections officers — throwing urine and feces at them before attacking them physically, according to Oliver. The corrections officers only suffered minor injuries.

The inmate responsible hasn’t been identified.

As for Hackett, he was denied bond shortly after his initial arrest in January and should remain in jail until his trial, which has yet to be scheduled. However, Prosecutors are charging him with two counts of capital murder related to Higby’s death, giving an indication they intend to seek the death penalty.

Because of the rules governing capital trials, Hackett’s defense has been provided up to $10,000 from the state to hire a mitigation expert in addition to other fees associated with his court-appointed public defenders.