zgrep -v "org" /path/to/files/* | zgrep "FollowEvent" | zgrep -o 'login":"[^"]*"' | cut -d'"' -f3 | sort | uniq -c | sed '1i{
       s/s*([0-9]*)s*(.*)/"2": 1,/;$a}' > usernames_followevents.txt

sed '1i{ s/s*([0-9]*)s*(.*)/"2": 1,/;$a}'