If you get this error when logged in as the user (it will show up for the user but not if you su as their user)
Neither the JAVA_HOME nor the JRE_HOME environment variable is defined
At least one of these environment variable is needed to run this program
Login as the user via SSH
Navigate to /home/user/tomcat/bin
Open startup.sh and shutdown.sh and add the following lines to the top:
export JAVA_HOME=/usr/local/java
export JRE_HOME=/usr/local/jdk
Then tomcat should start/stop just fine as them.