What exactly is a flash bang grenade and how does it work?

Mr. Onserio's arrest followed an altercation at Nairobi's Holy Family Basilica basement, according to multiple reports, with police officers being called in by the church guards over an alleged terror threat.

During the incident on Sunday morning, police officers searched his car and found a flash bang grenade and a pocket phone with the model number GA-25.

So what exactly is a flash bang grenade and how does it work? 

The flash bang grenade, also referred to as a stun grenade, is a non-lethal explosive that causes confusion in its target by exploding with an extraordinarily loud bang and bright lights.

It is similar to a standard grenade, but instead of a fuse, it has explosive powder inside. After being thrown, the grenade takes about 1.5 seconds to explode. A very bright flash and a loud sound (between 160 and 180 decibels) are produced when pyrotechnic chemicals based on magnesium explode.

They can temporarily impair vision and hearing, usually for a few seconds, and are frequently used by police to execute search warrants and control crowds.

In Kenya, no instances of the use of flash grenades have been reported.

The flash bang training unit model 7290T, made by Combined Tactical Systems, was the type of flash bang grenade discovered in the possession of the former Deputy Director of Communications at State House's Presidential Delivery Unit (PDU).

Although touted as non-lethal, these explosive devices have been known to cause death and serious injury, eliciting heated debate on their proper use. 

Some experts say that when used outdoors, flash-bangs can pick up gravel and launch it like shrapnel.

These explosive devices were initially developed by the British Special Air Service in the 1960s as training weapons, and they were later used for decades as military weapons. 

Mr. Onserio who is currently in custody, will be facing, among other charges, possession of explosives contrary to Section 6(1) as read together with Section 29 of the Explosive Act, Cap. 115 of the Laws of Kenya.