howling fit to kill

[jacdac]

Kevin Stoner sat in an empty office and waited for the inspector. The room was at the top of the stairs that led down to the custody suite. Through the slightly open door, Kevin could hear his ex-crewmate down below, howling fit to kill. His threats and obscenities resounded throughout the station.
Source: Murderer’s son by Joy Ellis
Context: Kevin’s ex-crewmate has been arrested for corruption.

What does the bolded expression mean?

Thank you.

 

[Trochfa]

In this context:
"howling" = shouting very loudly.
"fit to kill" = as if he was so angry he could kill someone.

 

[jacdac]

Thank you.