In my case, the tomcat.pid is under /opt/tomcat/temp/. Tried to delete it manually. Still didn't work. After check setnev.sh in /opt/tomcat/bin/, notice there is a line of code to define JAVA_HOME:
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.212.b04-0.el7_6.x86_64/jre
Commented out this line, restart Tomcat. It works! Since I did a yum update and a new minor version of Java update coming from 1.8.0.212 to 1.8.0.222. Lessons learned: Hard-code should be avoided.