My first thought about this was not terror, but criminals who are aliens, given the type of building and NYC demographics now.
I talked to an old gas fitter one time that said in the old days they would weld a flange on an active gas main then puncture it and quickly thread a pipe on it to add a new line.....not me.
Working with gas is simple, this is bizarre.
NYC is reaching the level of Nigeria. Poorly made Gas Line connections have killed far to many already for folks to not understand the risk.
If someone illegally tapped into the gas line, then why didn’t ConEd turn off the gas when they did the inspection that day?
When someone reports a gas leak, ConEd shuts off the gas to the entire building till the repairs are done.
According to the reports, the landlord was in the process of improving the gas line. The ConEd inspector failed to do a correct inspection if there was an illegal tapping. He should be investigated. Sometimes inspectors touch stuff they shouldn’t and cause more problems.
BTW, inspectors are not always very bright people.
As to the plumber, didn’t he smell the gas or know about opening a door while there’s a gas leak? This puzzles me.