Surveillance video shows murder suspect running from crime scene with weapons in hand

Spring, Texas – An arrest warrant has revealed new details about the arrest of a man accused of murder in Montgomery County.

The Montgomery County Sheriff's Office said 18-year-old Isaiah Mayham has been charged with murder in connection with the death of 19-year-old John Dennis Holmes III.

Holmes was found dead on July 16 in the middle of a street in the Spring neighborhood in the 300 block of Raypine Drive. He had suffered numerous gunshot wounds.

The warrant alleges Holmes communicated with someone on Instagram about meeting to exchange weapons. An associate of Holmes stated he wanted to purchase an assault pistol-style rifle (ARP) in exchange for a less valuable handgun and 20 grams of marijuana. Police believe the Instagram user Holmes communicated with was Mayham.

At about the time of the shooting, Holmes had planned to meet the consumer in the parking lot of an apartment complex to complete the deal.

When Holmes arrived, the user – presumably Mayham – asked him if he was alone and what vehicle he was in. Knowing Holmes was alone, investigators believed Mayham planned to carjack his car and rob him. Whether or not the murder was part of the plan at this point is unclear.

Surveillance footage from a neighboring apartment shows a man wearing a black hoodie with a bright pattern and blue jeans running away from the shooting. The man in the video appears to be holding two guns, one in each hand. One of the guns had a distinctive red magazine.

A search warrant obtained by Meta Platforms, the company that owns Instagram, uncovered information linking Mayham to the surveillance footage and the Instagram account Holmes used to communicate.

The search warrant included a photo of a firearm with a red magazine like the one the suspect was holding in the neighbor's surveillance video. Also found was a video showing a man wearing a black hoodie with a similar pattern to the one in the video. Another video taken after the shooting shows a man displaying a handgun with similar features to the one Holmes had before the attack.

As if that wasn't convincing enough, investigators have discovered an audio message from the account in which the speaker describes shooting Holmes and stealing his gun and marijuana. The speaker also says he burned the clothes he was wearing and wiped down the weapons used in the attack with alcohol.

Authorities identified the speaker in the audio message and other content collected from the account as Isaiah Mayham.

Mayham was further linked to the crime by GPS data. He had been released on bail by the Harris County Juvenile Probation Department on a murder charge in 2023. As a condition of his release, he was required to wear an ankle monitor, and the GPS data from that monitor beeped at the scene of the crime and showed him fleeing the area immediately afterward.

Officers initially arrested another 20-year-old man in connection with Holmes' murder, but video surveillance was used to prove that man's alibi.