DURHAM, N.C. -- A family received an anonymous "warning" letter in the mail after putting a sign in their yard.

They anticipated getting a letter from their homeowners association, but they didn't. This was a letter from a neighbor.

"It's disturbing to receive a letter like this," Marc Sprintz says. "It's like a non-threat, threat letter."

The Sprintz's sign says, "We believe Black lives matter, no human is illegal, love is love, women's rights are human rights, science is real, water is life. Injustice anywhere is a threat to justice everywhere".

The anonymous letter says, "You are asking for trouble and also going against the M/H sub-division covenants...This sub-division does not need to try and start a sign war that may lead to big problems...Black Lives Matter is racial and hatred to some whites."

The letter wraps up with, "Heed the warning, not a threat."

Kay Cee and Marc Sprintz are both teachers and say this is a teachable moment.

"We tell our students all the time that it's their job to speak their truth and to stand up for others," Kay Cee says. "And, when they see injustice occurring, that they need to say something and do something."

The Sprintzs have put a second sign in their yard in response to the letter. It welcomes neighbors with questions or concerns to come over and have a discussion.