Spawnkill Bug

[Shark_The_Helicopter]

Any idea what this is?

As you can see in the video. [RD] SniperPointer was paused.
 
Lax spawned a parachute which somehow made him bypass his own Spawn Protection and made the paused Pistol's Chainsaw Damage physical.

Although the chainsaw itself wasn't visible.

[Ege]

Probably he paused when his chainsaw was turned on, so it stayed working altough it might not seem like that in your screen. That used to be a way of abusing to kill someone especially while camping on towers. (I'm sure he didn't mean to do that so don't get me wrong like I'm blaming him)
As for Lax, using the command /para costs you 15 HP normally. However, if you use the command under spawn protection it just disables your protection instead of removing your HP. So he probably just kept typing /para everytime he respawned and ran into pistol's "working" chainsaw.

[Quido]

Pretty much what Ege said. Using /para whilst having spawn protection will remove it instead of decreasing your health by 15. Paused with the chainsaw active is the reason for the deaths.