(KRON) — Amtrak is no longer invited to BART’s 50th Anniversary celebration due to a Twitter trend that escalated into an online feud between the train services on Thursday. Here’s how it happened.

The trend broke out on Thursday, involving accounts tweeting out the most basic description of what they do. CNN tweeted “breaking news.” Papa Johns tweeted “pizza.” NASA tweeted “universe.” KRON4 even got in on the act.

Amtrak also joined the trend, tweeting, “trains.” However, BART had tweeted the same thing on July 15, 2020, and reminded Amtrak that they had the tweet idea first.

But who was really first in the grand scheme of things? Amtrak reminded BART that the first Amtrak train ran in 1971, while BART began service in 1972.

That tweet cost Amtrak its invitation to BART’s 50-year anniversary, which will be September 10 at the Lake Merritt station. BART is also offering half-off fares for the month to celebrate.

KRON4 is hoping that the train lines can reconcile their differences and get their relationship… back on track.