kill -pid

#!/bin/sh

enumerate_childs()
{
    local i

    for i in "$@"; do
        local childs="$(pgrep -d ' ' -P $i 2>/dev/null)"

        if [ -n "$childs" ]; then
            pids="$pids $childs"
            enumerate_childs $childs
        fi
    done
}

if [ $# -eq 0 ]; then
    echo "Nothing to kill"
    exit 0
fi

kpids="$@"

for p in $kpids; do
    enumerate_childs $p
done

kill -9 $kpids $pids