Error in killing Tshark from shell script

Question

I'm getting this error:

* glibc detected * /usr/sbin/tshark: double free or corruption

While doing as below, any idea why?

#!/bin/bash
trap 'my_exit; exit' SIGINT SIGQUIT
count=0

/usr/sbin/tshark -i bond1.1  -f "port 1111" -w /test/test_1.pcap > /dev/null 2>&1 &
PID1=$!

/usr/sbin/tshark -i bond1.6  -f "port 8080" -w /test/test_2.pcap > /dev/null 2>&1 &
PID2=$!

function my_exit()
{
    kill $PID1 
    kill $PID2 
}

while :
 do
   sleep 1
   count=$(expr $count + 1)
 done

BTW, When I try to run one tshark and kill it it works fine.